The present invention relates to a clamping collar suitable for fitting in a circumferential groove of a polymer duct to be connected to a nozzle for the transportation of a fluid, such a duct fitted with this collar and a method for blocking the rotation of this collar on this duct. The invention applies in particular to a pressurized hot air duct for a motor vehicle of a type made of plastic material and requiring a fitted metal collar, such as an outlet duct from a flow meter, supercharging air cooler or turbocharger, as nonlimiting examples.
Clamping collars intended to clamp a duct so it can be connected to a nozzle of a fluid transport system generally consist of a metal clamping strip fitted with a cage with a screw, also metal, forming the clamping member of this collar on a receiving groove of the duct. Once the collar is mounted in the groove, its rotational blocking relative to the duct is generally provided by the abutment of this cage against two short axial abutments projecting toward the interior of the groove from its respective rims.
A major drawback in the rotational blocking of known clamping collars lies in the inadequate nature of this blocking due to the small contact area between the collar and the duct receiving it.
Other drawbacks in the rotational blocking of these collars lie, on the one hand, in the risk of the holing of the duct made of plastic material by the metal cage of the collar leading to potential leaks of the fluid transported by this duct and, on the other hand, in the need to provide a minimum thickness for the groove rims in the abutment region and provide an accurate reclamping of the collar when it is fitted. In particular, use is usually made of greater thicknesses of plastic material in these rims to minimize their risk of holing by the cage which, in addition to the extra cost incurred for the manufacture of the duct, hampers the leak-tightness of the connection and also the fitting forces required.
The document FR A1 2 882 420 teaches rotationally blocking such a clamping collar between two abutments formed on one and the same lateral rim of the groove receiving it, via a metal blocking portion of square shape which extends axially, tangentially relative to the clamping strip, from the screw cage to which it is joined or from which it is distinct.
A major drawback of the collar equipping the duct according to this document is that the abovementioned risk of holing of the duct remains, given that the rotational blocking is obtained by a contact between the metal material of this blocking portion and the two groove rim abutments concerned. Another drawback in the blocking produced in this document lies in the large thickness of plastic material required to produce these two abutments, with the resulting abovementioned drawbacks.